Why is the second law of thermodynamics the only physical law that is time-reversal invariant?

The second law of thermodynamics, like no other physical law, defines a direction of time. All other laws are time-reversal invariant, meaning they are valid despite which direction time flows. Why is this so? What does this say about time?

It says very little about time. Instead, it points to the deficiencies in non-relativistic physics.

It is not the only law. There are interactions which cause time reversal violations.

neutral Kaon decay is one example. http://answers.yahoo.com/question/accuse_write?qid=20070119154004AAl3rL6&kid=PcBZIWrrOEsOE2EGOQH2&s=comm&date=2008-07-02+00%3A39%3A52&.crumb=

The expansion of the universe is a non-reversible process.

It isn't.

The uncertainty relation is also non reversible.

Mathematically it is because both are inequalities.

Philosophically it is because these two things are what drives the universe. Energy is conserved, so systems do not change because of energy but in order to increase entropy.